Communication techniques using visible light have been proposed. For example, as in Patent Literatures (PTLs) 1 and 2, there are proposals on a video display apparatus including a display, a projector, etc., to superimpose visible light communication information on normal video to be displayed and then display resultant video.
In addition, there are the digital watermark technology applied to printed materials, and techniques of displaying QR codes (registered trademark), barcodes, or the like, in images and using encoded signals thereof to spread information to the Internet world though imaging devices such as mobile phones, smart phones, or digital cameras.
However, in these techniques, video signals are displayed by way of driving each pixel and controlling a backlight, and as a part of the control on the backlight, the visible light communication signals are encoded and superimposed. Thus, these techniques can be applied only to video display devices which display video by controlling the two systems.
Another devised method is, for example, superimposing information on an entire image inconspicuously like watermark and decoding the superimposed information on a receiver side, that is, transmitting and receiving, in or without synchronization with video, information different from the video (e.g., information relevant to the video), using a video display apparatus. There has also been an approach that, as in press release 1, separates information quickly with use of an existing typical reception device although some deterioration is seen in video.